Apparatus for repairing defects in metallic workpieces by automatic means

ABSTRACT

The present invention relates to means for repairing defects in metallic workpieces, such as billets, which means are controlled by stored defect responsive information provided during the nondestructive test process. The nondestructive test apparatus provides defect responsive signals which are recorded and stored by storage means and subsequently recalled from the storage means for actuating defect repair means, such as a grinding wheel, engaging the workpiece at the defect location.

United States Patent Forster 51 July 18, 1972 [54] APPARATUS FORREPAIRING 3,180,230 4/1965 Judd et a] ..324 37 x DEFECTS IN METALLICWORKPIECES 3,262,123 7 1966 Crouch ..324/37 x BY AUTOMATIC MEANS3,290,167 12/1966 Wood et al.

3,394,302 7/1968 Judd [72] Inventor: Freiderich M. 0. Forster,Grathwohl- 3 4 9 1 2 9 19 9 w fl ct strasse 4, Reuflmgem Germany3,491,288 1 1970 Forster ..324 37 [22] FOREIGN PATENTS OR APPLICATIONS21 I 1 App] 50 458 1,177,328 5 1968 Great Br1ta1n ..51 165 R ForeignApplication Priority Data Sept. 13, 1969 Germany ..P 19 46 510.2

U.S.Cl ..51/165 R,5l/78,,90/11 R, 324/37 Int. Cl ..B24b 49/04 Field ofSearch ..51/165 R, 165.71, 165.72, 165.77, 51/74 R, 78; 324/37References Cited UNITED STATES PATENTS 2/1971 Miller et a1. ..324/379/1958 B0ltz..... 8/1961 Lloyd ..324/37 Primary Examiner-Lester M.Swingle Atl0rneyErvir1 B. Steinberg [57] ABSTRACT The present inventionrelates to means for repairing defects in metallic workpieces, such asbillets, which means are controlled by stored defect responsiveinformation provided during the nondestructive test process. Thenondestructive test apparatus provides defect responsive signals whichare recorded and stored by storage means and subsequently recalled fromthe storage means for actuating defect repair means, such as a grindingwheel, engaging the workpiece at the defect location.

5 Claims, 6 Drawing Figures PATENTEDJUHBIQTZ 3.676959 SHEET 1 OF 5FRIEDRICH M. O. FGRSTER INVENTOR.

PATENTEUJULIBIWZ 3.876359 SHEET 2 [1F 5 F l G 2 1 K 82 so 8 ]78FRIEDRICH M. o. F'CSRSTER INVENTOR.

PATENTED JUL 1 8 I972 FIG. 30

SHEET 3 UF 5 FRIEDRICH M. o. Fb'RsTER INVENTOR.

PATENTEU JUU 8 B72 SHEET U [1F 5 FRIEDRICH M. o. FO'RsTER INVENTOR.

APPARATUS FOR REPAIRING DEFECTS IN METALLIC WORKPIECES BY AUTOMATICMEANS This invention concerns an arrangement for repairing surfacedefects in a metallic workpiece for the purpose of preparing theworkpiece for further processing and to produce therefrom an end productof high quality. As used in the context of this invention, the termdefect" shall include, but not be limited to a crack, occlusion,inclusion, discontinuity and the like, the presence of which renders aworkpiece unsuitable or less desirable for further processing, such asrolling or drawing, and which defect ultimately may result in a rejectedend product, or one characterized by inferior quality. Moreover, therepair of defects shall include a means for operating on the location ofa defect, and such repair being adapted to prevent, when the workpieceis processed further, a degradation of the quality or a defective endproduct due to a heretofore existing defect.

When manufacturing wire, for example, an inclusion extending over arelatively short distance is increased during the drawing process toseveral times its original length. Thus, as a workpiece during drawingis subjected to high stress, a crack of considerable length may beproduced and such a defect may very likely decrease the quality of thewire or render the particular wire portion not useable.

Apparatus have become known in which current is passed through aferromagnetic workpiece, such as a steel billet. A defect along thelongitudinal axis of the workpiece causes magnetic leakage flux at thelocation of such defect. The leakage flux is transferred to a magneticrecording belt .which is brought into contact with the surface of theworkpiece under test. A sensing device responsive to the magnetic fieldis disposed for scanning the surface of the belt and provides a defectresponsive electrical signal which can be displayed on the screen of acathode ray tube. This described arrangement is known as themagnetographic test method.

An apparatus of this type may be operated in such a manner that thewidth of the billet to be tested is divided into several zones, forinstance four zones, and that a respective marking device is providedfor each zone. Upon the discovery of a defeet, the respective markingdevice causes a mark to be affixed to the workpiece at the location ofthe defect. Such marking may be accomplished, for instance, by a spraynozzle which is energized to produce a painted line whose lengthcorresponds to the length ofthe defect.

Moreover, there are apparatus in which the workpiece is fed through acoil which is excited with alternating current of suitable frequency.The electrical field causes eddy currents in the workpiece. Theexistence of a defect manifests itself as a particular effect upon thecoil and the existence and size of such a defect can be ascertained. Itis known further that such an apparatus may be combined with a markingdevice for affixing at the location of the defect a mark ofpredetermined size and the extent ofsuch mark can be made to correspondto the defect.

Further arrangements have been disclosed which make use of eddy currentsensing devices which rotate about a workpiece as eddy currents aregenerated within the workpiece. Again, a defect within the workpiece issensed by the probes and a marking device is actuated in response to adefect being sensed.

With the above described arrangements it has been possible todistinguish between large and small defects and decide whether themarked workpiece should be rejected, or whether the defect can berepaired or remedied by localized treatment. Such repair may be carriedout somewhat later but must be done before a finished end product isprovided. A defect may be repaired, for instance, by grinding theworkpiece with a portable grinding wheel. To date, the repair ofdefects, known generally as cleaning, has been carried out mostlymanually.

The described method of repairing a defect is afflicted with severalshortcomings. Firstly, such cleaning constitutes an additional operationduring fabrication and, being a manual process, requires considerableamount of time. For instance,

when cleaning steel billets, it may be necessary to clean consecutivelyfour different sides and it will be necessary, therefore, to rotate thebillet each time. A further disadvantage resides in the fact that thegrinding installation usually is not located along the production linewhere the workpiece is fabricated, hence transportation problems arise.Also, the repair of the defect depends to a considerable extent on theworker and his diligence whether or not all marked locations areproperly repaired. In many cases the defect is not apparent by visualobservation and considerable judgment on the part of the worker isrequired in deciding the depth to which the repair must be extended.

The present invention is an outgrowth of the need for overcoming thedescribed shortcomings. According to the present invention, an apparatusis described for the repair of defects in metallic workpieces, Theapparatus comprises a nondestructive test arrangement having one or moretest channels, each associated with a predetermined zone of theworkpiece. The test arrangement is adapted to provide a defectresponsive impulse when and for the duration that the size of a defectexceeds a predetermined limit. Each channel is coupled to the storagedevice for temporarily storing a defect responsive signal, the locationof the signal in the storage device being correlated with the defect inthe workpiece. A defect repair means is associated with each of thechannels and coupled to be responsive to the signal condition of thestorage device. The storage device is cyclically interrogated and uponthe existence of a defect responsive signal, the repair means is actatedto cause in an automatic manner the repair of the defect present in theworkpiece.

It is not important which type of storage means is used. In the simplestembodiment, as will be explained by an example, if the defect is markedby applying paint upon the workpiece, the workpiece itself mayconstitute the storage means. In all cases when signal storage is used,the defect responsive signal is stored in digital form and the presenceor absence of such a signal is used to indicate whether or not a defectabove a predetermined level exists. Similarly, the type of the repairmeans is immaterial and the present invention permits the use of a greatvariety of repair means which may be used advantageously.

Also, the invention is not limited to a specific type of workpiece. Forinstance, the invention may be used advantageously for billets ofrectangular, round or other cross-section.

The invention will be more clearly apparent by reference to thedescription in which:

FIG. 1 depicts an apparatus for the repair of defects in a billet usingan electronic shift register as a storage means;

FIG. 2 depicts an apparatus for the repair of defects in a billet usinga magnetic recording tape as a storage means;

FIGS. 3a and 3b depict an apparatus for the repair of defects in abillet using a magnetic recording tape as a storage means and enablingthe repair of defects to be carried out sub- 7 sequently at a suitabletime and place;

FIG. 4 depicts an apparatus for the repair of defects in a billetwherein the markings affixed to the billet are used as storage means,and

FIG. 5 depicts an apparatus for the repair of defects in a billet usinga single grinding wheel for the removal of defects.

As shown in FIG. 1, the nondestructive test apparatus comprises amagnetographic device which is used for testing billets, see forinstance U.S. Pat. No. 3,491,288 in the name of F. M. O. Forster, datedJan. 20, 1970. A billet 2 to be tested is magnetized by electric currentbeing passed therethroughlengthwise. Longitudinal cracks 4 within thebillet 2 intersect the magnetic field 6 formed about the circumferenceof the billet and cause the existence of a magnetic stray field 8 at thetacted by the belt. In this manner there is provided a continuousrecording of the defect responsive magnetic stray fields. As viewed inthe direction of rotation of the magnetic belt 10, a scanning disk 16 isdisposed to engage the entire width ofthe belt along the line 14 afterthe latters contact with the surface of the billet 2. A magnetic sensingmeans 18 for sensing the signals on the belt 10 is disposed on theperiphery of the scanning disk 16 which is driven by a motor 17. Anerasing means 34 is disposed so that signals stored on the rotating beltare erased prior to renewed contact of a belt portion with the surfaceof the billet, thus rendering the recording means suitable for recordingthe subsequent signals. The sensing means 18 is coupled via acontactless or rotating transformer 19 to a logic circuit 20 whichamplifies the defect responsive signals, causes demodulation thereof andcontains, moreover, in its output stage a trigger circuit which providesan output signal if the defect responsive signal exceeds a predeterminedvalue. The output of the logic circuit 20 is coupled to the input of anelectronic channel gate 21.

The scanning disk 16 is provided with four permanent magnets 22, 23, 24and 25 which cause a respective impulse to be generated by thestationary coil 27 as a respective magnet passes in front of the coil.The distance between the magnets 22, 23, 24 and 25 is selected in such amanner that the distance between the respective magnets corresponds tothe width of the zones 30, 31, 32 and 33 into which the surface of thebillet is divided. It is necessary, therefore, that the arrangement issuch that the first permanent magnet 22 reaches the coil 27 at the verymoment when the sensing means 18 is positioned adjacent the near edge ofbelt 10. This condition corresponds to the sensing ofa signaloriginating at the beginning of the zone and stored on the belt 10.

A signal generated by the coil 27 is amplified by the amplifier 28 andis used as a command signal coupled to the input 29 of the channel gate21. The command signal 50 produced causes the channel gate to bepositioned in such a condition that a signal received at the input 26 iscoupled to the output 36.

If the sensing means 18 is positioned for receiving a signal from thebelt 10 corresponding to the zone 31, the magnet 23 causes the coil 27to receive a subsequent impulse, which signal after being amplified bythe amplifier 28 causes actuation of the channel gate 21 and provides acircuit connection between the input 26 and the output 38.

Subsequent to the scanning of that portion of the recording belt 10which corresponds to the last zone 33, at which time the input 26 of thechannel gate 21 is coupled to the output 42, a new counting cycle isstarted so that the following impulse at the input 29 of the channelgate 21, signifying the start of a new scanning cycle, causes the input26 to be coupled to the output 36.

In this manner the four zones 30, 31, 32 and 33 are associated with theoutputs 36, 38, 40 and 42 of the channel gate 21 to form four testchannels.

The outputs 36, 38, 40 and 42 of the channel gate are coupled to storagemeans such as the four storage channels 44, 46, 48 and 50. Each channelcomprises a stepping or shift register. The registers contain a seriesof n serially coupled stages or positions which are adapted to storesignals in binary form and which signals, in this instance, denotedefect or no defect.

Corresponding to the translating motion of the billet 2, the storedinformation is stepped or shifted from position to position. The outputposition of each storage means (shift register) is coupled to arespective repair means 52, 54, 56 and 58. As viewed in the direction ofmotion'of the billet, the means adapted to cause the repair ofa defectare staggered in the respective zones 30, 31, 32 and 33 by apredetermined distance with respect to the test location 60.

For the sake of simplicity, it is assumed that the distance between thetest location 60 and the line 14 along the belt 10 is so short comparedto the distance .4 between the test loca tion 60 and the location of therearmost defect repair means 74 that it can be neglected. Moreover, itwill be assumed that the distance A is divided into n divisions. Aroller 62 driven by the moving billet 2 is provided at its peripherywith permanent magnets 64 whose spacing from each other corresponds tothe length of such divisions A/n. Opposite the permanent magnets thereis disposed a stationary induction coil 66 which produces a pulse signalresponsive to the translation of the billet by a division 14/11. Theoutput of the induction coil 66 is connected to the command signal inputof each storage means 44, 46, 48 and 50. In this manner, as disclosedheretofore, the stored information is shifted from position to positionin synchronism with the motion of the billet by a distance A/n.Therefore, the defect information is shifted in step with the motion ofthe billet, or expressed in other terms, the defect information isshifted together with the moving defect and arrives at the locationwhere the repair can be made concurrently with the defect. A signalcorresponding to a defect disposed in the output position of aparticular storage means caused operation of the associated repair meansand the repair means remains actuated as long as such a signal ispresent. If a crack has a certain length and such length extends overseveral distance divisions A/n, the repair means remains actuated untila defect-free distance or division appears. As illustrated, the meansfor repairing defects may comprise grinding wheels 68, 70, 72 and 74,each disposed above a respective zone of the billet 2. Upon receipt of adefect responsive output signal from .the storage means, a respectivegrinding wheel is activated and lowered upon the billet for repairingthe defect.

If further storage means are provided which are responsive to otherdefect information, eg information corresponding to the defect depth, itwill be possible to provide operation of the grinding wheelcorresponding to the depth of the defect. In practice it has been foundthat a single depth setting is suffcient for a majority of cases.

Owing to the large dimension of the grinding wheels it is not possibleto dispose these wheels side by side at the location of defect repair,rather they must be staggered along the length of billet motion. Thus,only the rearmost grinding means 58 is coupled to the last or n'"position of the associated shift register. The next-preceding grindingwheel is distanced forwardly by a multiple integer a of the division A/nand, in order that this last-mentioned wheel receives its actuatingsignal at the proper moment, it must be connected to the (n-a) positionof the associated storage means. A similar condition must prevail forall of the other serially disposed grinding means.

In certain instances, billets are tested simultaneously along all foursides. It is readily possible then to provide for the defect repair onall four sides. In this latter example it will be necessary, of course,to dispose grinding wheels along the four billet sides using thedisclosed method. Such an arrangement has the major advantage that thebillet passes through the test apparatus in a single path and leaves theapparatus fully cleaned.

Itshould be understood that the magnetographic test apparatus used inthe heretofore described embodiment may be replaced by anothernondestructive test device, for instance eddy current by stray flux testmeans using either a rotating probe for round material or areciprocating probe for rectangular or flat stock.

The above described invention is not limited to the use of a storagedevice in the form of a shift register. It may be advantageous, forinstance, to use a track on a magnetic recording tape 88, see FIG. 2,for each of the test channels 36, 38, 40 and 42.

In this example the defect responsive signal of each test channel 36,38, 40 or 42 is coupled to a respective head 71, 73, 75 or 77 forrecording the respective signals on a track of the magnetic tape 88. Thetape 88 has a speed governed by the translational speed of the billet 2.The recording tape transport and the billet motion provided by roller 86may be coupled to each other via entirely mechanical means. However, aSelsyn drive may be found suitable also. In both cases, it will not benecessary that the speed of the billet and that of the recording tape beidentical, the only requirement being that they are in proportion.Assuming the h denotes a given distance of the billet, s denotes thecorresponding distance along the recording tape, v denotes the speed ofthe billet, and v, the speed of the recording tape, then h'v, s'v,. Adistance S separates the signal retrieving means or pickup heads 78, 80,82 and 84 from the recording heads 71, 73, 75 and 77 associated with thetape 88. The pickup heads sense the recorded defect signals and actuatein response thereto the defect repair means 52, 54, 56 and 58. Thedistance S, is dependent upon the distance A which denotes the distancebetween the defect sensing location and the repair means. From the aboveformula it follows that S, A'v /v An interesting modification involvingthe use of a recording tape in conjunction with the present invention isshown in FIGS. 3a and 3b. This modification concerns the read-out of thedefect responsive signals recorded on tape 88 at a selected time andplace. To this end, the billet 2 and the tape 88 are transportedtogether to another location, such as a cleaning installation, where thedefects are repaired fully automatically. In order to proceed inaccordance with this modification it will be necessary to provide ameans for transporting the billet (not illustrated), a tape transportmeans 89 for the tape 88, pickup heads 78, 80, 82 and 84, and defectrepair means 52, 54, S6 and 58. As described hereinabove, the speed ofthe tape over the roller 86 is controlled by the translational speed ofthe billet. The location of the defect repair means is governed by theabove stated formula in an analogous manner.

Another interesting modification of the present invention is shown inFIG. 4 and uses the billet itself as the means for recording and storingthe information. Similarly as above, the defects may then be repaired ata selected time and location. This modification obviates the need for aseparate storage means. It is assumed that during the nondestructivetesting process of the billet paint marking is applied to the billet inresponse to defects sensed. The paint marks denote the location of thedefect and indicate that a defect exceeds a predetermined minimum value.Testing and marking may be carried out using a plurality of channels,for instance four channels corresponding to zones 30, 31, 32 and 33 ofthe billet. The object tested, for example, may be once again the side12 of the steel billet 2. Four light sensitive means, such asphotodiodes 90, 92, 94 and 96, are disposed along the direction ofmotion of the billet 2 above the side 12 of the billet to be cleaned,and one diode is associated with each respective zone 30, 31, 32 or 33.A source of light 98 illuminates the surface portion-of the billetdisposed opposite the photodiodes. If a paint mark is present, therespective photodiode receives the reflected light and provides anoutput signal. in order to exclude spurious light, the photodiodes maybe provided with filters which preferably pass only reflected lightoriginating from a paint mark. The output signals from the diodes arepassed to respective amplifiers 91, 93, 95 or 97, one amplifier for eachdiode, which in turn are connected to the means for providing for therepair of defects, the grinding wheel means 52, 54, S6 and 58. If apaint mark 100 appears underneath the photodiode 92, a short time delayis provided which corresponds to the transit time of the defect from thephotodiode 92 to the grinding wheel 70 before the grinding wheel isactivated. The grinding wheel remains energized so long as a paint markis sensed underneath the photodiode.

Often there is a desire that the paint be not visible with the nakedeye. In this case it will be possible to provide instead of a normallyused paint an organic liquid of high volatility having dispersed thereinfluorescent particles. An ultraviolet lamp is used then in place of theconventional lightsource 98. Moreover, spurious light may be excludedeven further by using photosensitive means which have maximum spectralsensitivity in the ultraviolet energy spectrum..Additionally,ultraviolet light filters may be used in front of the photodiodes. Theabove description has dealt largely with the use of grinding means forrepairing defects. However, the repair or cleaning may be accomplishedalso by other means, such as chiselling or milling. Heating of thedefect location using a torch as known in welding is another methodwhich may be used advantageously. In this example, the output of thestorage means controls the gas flow and ignition. A very fast action ispossible for repairing with a high degree of success even small defectsdespite a relatively rapid billet motion.

Plasma heating may be substituted for chemically fueled flames in orderto obtain localized melting.

Finally, a further modification of the present invention is possible. Inthis modification a single defect repair means, such as a grindingwheel, is useable in conjunction with the defect responsive signalsprovided by a plurality of test channels. As seen for example byreference to FIG. 5, the defect information provided by a nondestructivetesting apparatus having a plurality of test channels is available inthe form of zoned paint markings associated with the respectivechannels, there being four zones on the face of the billet 2 asdescribed previously. The defect repair means comprises a grinding wheel102 which may be moved in a transverse direction across the billet to arespective test zone which corresponds with the width of the respectivetest channel. Furthermore, the grinding wheel may be reciprocatedlengthwise along billet 2 to provide for the repair of defects locatedin a particular zone. The arrangement includes a carriage 126, a motivemeans 117 for moving the carriage along the billet, a set of fourilluminating means 112, 114, 116 and 118, one illuminating means forilluminating a respective zone 30, 31, 32 and 33, four associatedphotodiodes 104, 106, 108 and 110, all mounted to the carriage anddisposed above the billet face. The lengthwise motion of the carriage islimited by a pair of light gates 120 and 122 which are connected to anelectronic control circuit 124 for controlling the motion of the motivemeans 117. The grinding wheel 102 is also mounted upon the carriage andis adapted to be moved across the face of the billet to the differentz'ones responsive to the motion of the motive means 119 which iscontrolled by the control circuit 124 to which the illuminating meansand photodiodes are coupled for controlling the position and actuationof the grinding wheel. When the motive means 117 controlling'thelengthwise motion of the carriage 126 is started, the grinding wheel 102is disposed in the outermost left zone. The grinding wheel is coupledvia the control circuit 124 to the diode associated with that respectivezone, specifically in this case with the photodiode 104. Whenencountering the defect marking 128, the grinding wheel is actuated andcleans the defect location. As the carriage passes to the light gate120, the longitudinal carriage motion is terminated, the transversegrinding wheel motion is initiated, and the carriage return motionprepared. The defect information received by the photodiodes 106, 108and 110 during the preceding longitudinal carriage motion is stored bythe control circuit. Zones in which no defect was present are skippedduring the transverse motion of the grinding wheel so that after thegrinding wheel is positioned in a new zone and the carriage is returnedin response to such positioning, only the next zone exhibiting a defectmarking is being worked. When the carriage reaches the opposite end ofits longitudinal travel the described procedure is repeated until alldefects marked by paint on the respective billet face are repaired.

It will be apparent that there exist still further embodiments of thisinvention which have not been described. The above examples are merelyillustrative of the advance achieved in the art by combining thenondestructive test method carried out on billets with automatic defectrepair means.

What is claimed is:

1. An apparatus for repairing defects in a billet comprising:

A. means for subjecting a billet to translating motion and passing itsequentially past a magnetographic test device and a repair stationspaced a predetermined distance from one another;

B. said magnetographic test device including:

1. magnetic recording means having an endless belt;

2. means for rolling said belt longitudinally along the surface of thebillet as the billet is translated past said test device, said means forrolling causing a portion of said belt to be in contact with saidsurface, whereby magnetic stray fields responsive to defects in thebillet manifest at said surface are recorded upon said belt;

. a rotatable scanning disk disposed to engage the width of said beltalong a line transverse to the motion of the billet between said deviceand said station, said scanning disk being disposed to be in contactwith a portion of said belt after such portion has been in contact withsaid surface;

4. motive means coupled for rotating said disk about its center; I

5. a sensing means disposed at the periphery of said disk for receivingsignals responsive to the recorded stray fields on said belt as saidsensing means passes over said belt;

C. means disposed for erasing the recordings on said belt after saidbelt has been scanned by said sensing means;

D. a shift register which includes an input means, an output means and aplurality ofserially coupled stages connected therebetween;

E. means coupling said sensing means to said input means of said shiftregister;

F. repair means adapted to operate, when actuated, on the billetdisposed at said repair station and coupled to said output means, and

G. means responsive to the translational motion of the billet coupled tosaid shift register for providing a control signal which causes saidstages to shift a received signal from said input means to said outputmeans in step with the motion of a defect in the billet from said testdevice to said repair station for causing actuation of said repair meanswhen such defect is disposed at said repair station.

2. An apparatus for repairing defects in a billet as set forth in claimI, said billet having at least one flat surface, said endless belt beingin contact with said flat surface, and said repair means disposed toengage said flat surface.

3. An apparatus for repairing a defect in the surface of an elongatebillet, said surface being divided into a plurality of parallellongitudinal zones comprising:

A. means for subjecting the billet to continuing translating motion forpassing it sequentially past a magnetographic test device and a repairstation spaced a predetermined distance from one another;

B. said magnetographic test device including:

1. magnetic recording means having an endless belt;

2. means for rolling said belt longitudinally along said surface of thebillet as the billet is translated past said test device, said means forrolling causing a portion of said belt to be in contact with atransverse portion of said surface spanning said zones, whereby magneticstray fields responsive to defects in the billet manifest at saidsurface portion are recorded upon said belt portion;

. a rotatable scanning disk disposed to engage the width of said beltalong a line transverse to the motion of the billet between said deviceand said station, said scanning disk being disposed to be in contactwith a portion of said belt after such portion has been in contact withsaid surface;

4. motive means coupled for rotating said disk about its center;

5. a sensing means disposed at the periphery of said disk for producingsignals responsive to the recorded stray fields on said belt as saidsensing means passes over said belt;

C. means disposed in proximity to said belt for erasing the recordingson said belt after said belt has been scanned by said sensing means;

D. a shift register which includes a plurality of channels correspondingto the quantity of zones, each channel being associated with arespective zone and havingan input means, an output means and aplurality of serially coupled stages connected between the respectiveinput means and output means;

E. a gate means coupled to said shift register input means;

F. means coupling said sensing means to said gate means;

G. control means associated with said disk and coupled to said gatemeans to cause during rotation of said disk signals produced by saidsensing means to be transferred to the respective channel which isassociated with the zone having the defect which causes the existenceofsuch signal;

H. said repair station including a plurality of independently operablerepair means, one for each of said zones, and each such repair meansincluding means for actuating the associated repair means to cause therespective repair means to operate upon the surface portion of thebillet of the associated zone;

1. means coupling each of said means for actuating to the output meansof the associated channel, and

.1. further control means disposed for engaging the billet and coupledto each of said channels for providing a cyclic control signalcorresponding to the translational motion of the billet for causing saidstages to shift a received signal from the respective input meansthrough the associated stages to the output means in step with thetranslating motion of the billet, to cause actuation of the respectiverepair means when a defect disposed in the respective zone of the billetas originally recorded by said belt is disposed for repair by suchrespective repair means.

4. An apparatus for repairing defects in a billet as set forth in claim3, said repair means comprising grinding means, said grinding meansbeing disposed in a staggered array in the respective zones, thelongitudinal distance between two adjacent grinding means being theratio ofa-A/n wherein:

a is a multiple integer of the ratio A/n; 1

A equals the distance between said belt and billet surface and theposition of the rearmost grinding means;

n is the quantity of serially coupled stages of the register channelassociated with the rearmost positioned grinding means and is equal alsoto a selected quantity of longitudinal distance increments of the billetinto which the distance A is divided; and means causing said furthercontrol means to provide said cyclic control signal whenever the billethas moved by a distance increment A/n.

5. An apparatus for repairing defects in a billet as set forth in claim3, and amplifier means including means coupled in circuit with saidsensing means and said gate means for providing a signal to said gatemeans when a signal produced by said sensing means exceeds apredetermined value.

1. An apparatus for repairing defects in a billet comprising: A. means for subjecting a billet to translating motion and passing it sequentially past a magnetographic test device and a repair station spaced a predetermined distance from one another; B. said magnetographic test device including:
 1. magnetic recording means having an endless belt;
 2. means for rolling said belt longitudinally along the surface of the billet as the billet is translated past said test device, said means for rolling causing a portion of said belt to be in contact with said surface, whereby magnetic stray fields responsive to defects in the billet manifest at said surface are recorded upon said belt;
 3. a rotatable scanning disk disposed to engage the width of said belt along a line transverse to the motion of the billet between said device and said station, said scanning disk being disposed to be in contact with a portion of said belt after such portion has been in contact with said surface;
 4. motive means coupled for rotating said disk about its centEr;
 5. a sensing means disposed at the periphery of said disk for receiving signals responsive to the recorded stray fields on said belt as said sensing means passes over said belt; C. means disposed for erasing the recordings on said belt after said belt has been scanned by said sensing means; D. a shift register which includes an input means, an output means and a plurality of serially coupled stages connected therebetween; E. means coupling said sensing means to said input means of said shift register; F. repair means adapted to operate, when actuated, on the billet disposed at said repair station and coupled to said output means, and G. means responsive to the translational motion of the billet coupled to said shift register for providing a control signal which causes said stages to shift a received signal from said input means to said output means in step with the motion of a defect in the billet from said test device to said repair station for causing actuation of said repair means when such defect is disposed at said repair station.
 2. means for rolling said belt longitudinally along the surface of the billet as the billet is translated past said test device, said means for rolling causing a portion of said belt to be in contact with said surface, whereby magnetic stray fields responsive to defects in the billet manifest at said surface are recorded upon said belt;
 2. means for rolling said belt longitudinally along said surface of the billet as the billet is translated past said test device, said means for rolling causing a portion of said belt to be in contact with a transverse portion of said surface spanning said zones, whereby magnetic stray fields responsive to defects in the billet manifest at said surface portion are recorded upon said belt portion;
 2. An apparatus for repairing defects in a billet as set forth in claim 1, said billet having at least one flat surface, said endless belt being in contact with said flat surface, and said repair means disposed to engage said flat surface.
 3. An apparatus for repairing a defect in the surface of an elongate billet, said surface being divided into a plurality of parallel longitudinal zones comprising: A. means for subjecting the billet to continuing translating motion for passing it sequentially past a magnetographic test device and a repair station spaced a predetermined distance from one another; B. said magnetographic test device including:
 3. a rotatable scanning disk disposed to engage the width of said belt along a line transverse to the motion of the billet between said device and said station, said scanning disk being disposed to be in contact with a portion of said belt after such portion has been in contact with said surface;
 3. a rotatable scanning disk disposed to engage the width of said belt along a line transverse to the motion of the billet between said device and said station, said scanning disk being disposed to be in contact with a portion of said belt after such portion has been in contact with said surface;
 4. motive means coupled for rotating said disk about its centEr;
 4. motive means coupled for rotating said disk about its center;
 4. An apparatus for repairing defects in a billet as set forth in claim 3, said repair means comprising grinding means, said grinding means being disposed in a staggered array in the respective zones, the longitudinal distance between two adjacent grinding means being the ratio of a.A/n wherein: a is a multiple integer of the ratio A/n; A equals the distance between said belt and billet surface and the position of the rearmost grinding means; n is the quantity of serially coupled stages of the register channel associated with the rearmost positioned grinding means and is equal also to a selected quantity of longitudinal distance increments of the billet into which the distance A is divided; and means causing said further control means to provide said cyclic control signal whenever the billet has moved by a distance increment A/n.
 5. An apparatus for repairing defects in a billet as set forth in claim 3, and amplifier means including means coupled in circuit with said sensing means and said gate means for providing a signal to said gate means when a signal produced by said sensing means exceeds a predetermined value.
 5. a sensing means disposed at the periphery of said disk for producing signals responsive to the recorded stray fields on said belt as said sensing means passes over said belt; C. means disposed in proximity to said belt for erasing the recordings on said belt after said belt has been scanned by said sensing means; D. a shift register which includes a plurality of channels corresponding to the quantity of zones, each channel being associated with a respective zone and having an input means, an output means and a plurality of serially coupled stages connected between the respective input means and output means; E. a gate means coupled to said shift register input means; F. means coupling said sensing means to said gate means; G. control means associated with said disk and coupled to said gate means to cause during rotation of said disk signals produced by said sensing means to be transferred to the respective channel which is associated with the zone having the defect which causes the existence of such signal; H. said repair station including a plurality of independently operable repair means, one for each of said zones, and each such repair means including means for actuating the associated repair means to cause the respective repair means to operate upon the surface portion of the billet of the associated zone; I. means coupliNg each of said means for actuating to the output means of the associated channel, and J. further control means disposed for engaging the billet and coupled to each of said channels for providing a cyclic control signal corresponding to the translational motion of the billet for causing said stages to shift a received signal from the respective input means through the associated stages to the output means in step with the translating motion of the billet, to cause actuation of the respective repair means when a defect disposed in the respective zone of the billet as originally recorded by said belt is disposed for repair by such respective repair means.
 5. a sensing means disposed at the periphery of said disk for receiving signals responsive to the recorded stray fields on said belt as said sensing means passes over said belt; C. means disposed for erasing the recordings on said belt after said belt has been scanned by said sensing means; D. a shift register which includes an input means, an output means and a plurality of serially coupled stages connected therebetween; E. means coupling said sensing means to said input means of said shift register; F. repair means adapted to operate, when actuated, on the billet disposed at said repair station and coupled to said output means, and G. means responsive to the translational motion of the billet coupled to said shift register for providing a control signal which causes said stages to shift a received signal from said input means to said output means in step with the motion of a defect in the billet from said test device to said repair station for causing actuation of said repair means when such defect is disposed at said repair station. 